Approximately 21% of HIV infections in the U.S. are undiagnosed, but only about 40% of all adults have been tested. Thus, late diagnosis of HIV is common, and, furthermore, treatment delays and disruptions are widespread. Heterosexuals at high risk (HHR) are significantly less likely to test for HIV, are more likely to be diagnosed with HIV late, and experience serious barriers to entering care compared to other groups. Our research team has studied HHR in New York City (NYC) as part of the CDC's National HIV Behavioral Surveillance (NHBS) studies. We found an HIV prevalence rate of 7.4% among HHR in NYC, and only 6% of these infections had been previously diagnosed. Further, in central Brooklyn, 10% were newly diagnosed with HIV. The proposed study will use NHBS methodology to target HHR. Reduced rates of HIV testing and treatment among HHR are due to structural (e.g., poor access), social (e.g., peer norms), and individual-level (e.g., low perceived risk) barriers. Thus active recruitment approaches modeled after NHBS are needed to overcome structural barriers, and peer-delivered interventions effectively reduce individual and social barriers to testing and treatment. The primary goal of the proposed study is to evaluate the efficacy of a multi-level enhanced peer-driven intervention (PDI) to seek, test, treat and retain HHR. The enhanced PDI is tailored specifically for HHR and includes computerized, navigation, and peer-delivered components to enhance future sustainability. The design of the intervention is guided by the Theories of Triadic Influence and Normative Regulation. Similar to NHBS, the enhanced PDI will use respondent-driven sampling (RDS). NHBS protocols use both venue-based sampling (VBS) and RDS for reaching populations at high risk. However, VBS and RDS have not yet been directly compared in terms of their yield of undiagnosed HIV infections. Thus the specific aims of this five-year proposed study are to: (1) compare the yield and efficiency of RDS and VBS to identify undiagnosed HIV infection among HHR; (2) measure the efficacy of an enhanced PDI compared to a control in terms of time to HIV care and HAART initiation, viral load suppression, and retention among those newly diagnosed; (3) examine whether the effects of the PDI on HIV health/treatment outcomes are mediated by changes in individual (e.g., perceived risk), social (e.g., peer norms), and structural influences (e.g., enhanced access), and/or whether other factors (e.g., substance use) moderate its effects; and (4) to project the costs and cost-effectiveness of RDS vs. VBS and PDI. We will conduct the enhanced PDI (N=3000) in central Brooklyn, a location hyperendemic for HIV and where HHR experience poor access to testing and treatment. Simultaneously, VBS (N=400) will be undertaken in central Brooklyn. The proposed study complements local and national HIV prevention initiatives and is designed to contribute an efficient, innovative, and sustainable multi-level recruitment approach and intervention to the HIV prevention portfolio. The vast majority of HHR are African-American or Latino; therefore the proposed study may also impact racial/ethnic disparities in HIV/AIDS.